1. Field of the Invention
This invention relates to cardiac pacers and more particularly to improvements in digital circuit means for generating cardiac stimulation pulses.
2. Description of the Prior Art
Berkovits U.S. Pat. No. 3,345,990 employs a pair of thyratrons for disabling the transmission of a generated pulse to the heart during intervals when the circuitry detects an R-wave produced by the heart. Previous demand circuitry had used other approaches for responding to the signals from normal heart operation.
Keller U.S. Pat. No. 3,557,796 describes a demand heart pacer comprising a clock, a counter generating pulses at a rate appropriate for cardiac stimulation signals, circuit means detecting signals from the heart, noise discrimination counters in such heart signal detection circuit means, and coupling means for disabling such cardiac stimulating signals when appropriate naturally occurring heart signals are detected.
Gobeli U.S. Pat. No. Re. 28,003 describes a pacer which, when subjected to electromagnetic interference, operates at a rate different than its normal demand rate.
Greatbatch U.S. Pat. No. 3,870,050 describes a demand cardiac pacer comprising a clock, a counter, and means inhibiting the transmission of signals from the counter whenever an appropriate signal is detected from normal operation of the heart.
Although digital pacers have been proposed, cardiologists have persisted in making more extensive use of other types of pacers.